I really like this type of innovation, but I don't understand this defense against "vote buying." Can't the vote purchaser require the voter to take a picture of the completed ballot with their camera? That's a pretty easy way to verify if they followed through on their vote. I do like all of the other transparency issues and checking your voting results online though.
I've been hoping for a cryptographic solution to the question of vote-counting integrity for a long time. This looks really promising (and, possibly, affordable). Hopefully we'll see wide adoption of systems like this, and can toss Diebold machines like the trash that they are.